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Every time BMI is mentioned someone has to come up with an example of a body builder or fit athlete who has a high BMI. Yes, everyone realizes this already, and

Every time BMI is mentioned someone has to come up with an example of a body builder or fit athlete who has a high BMI. Yes, everyone realizes this already, and nobody who is in that position is going to be mislead into thinking they are obese. Sure, it would be great if everyone could do a caliper test or a water displacement test, but that isn't ever going to happen, and BMI is a trivial and good enough place to start. Because being overweight/obese is normalized because it is seen everywhere, there are tens of millions of people who have no idea they are at an unhealthy weight ... they rightly think they look like everyone else. The BMI is a an easy metric to get people to evaluate if they need to do something about it.

kbenson 6y ago
> Yes, everyone realizes this already, and nobody who is in that position is going to be mislead into thinking they are obese. No, but someone who works out the numbers and realizes that the BMI doesn't match them well, or their circumstances well, realizes it calls the study and what it represents into question. Using controversial metrics because they are easily available is counter-productive in the long run, because once people realize you were misrepresenting your credibility is lost. At best it's lazy. Right now I'm obese. In high school according to the BMI I was almost half-way through overweight edging towards obese, and that was with very little fat, a very active lifestyle, and a visible six-pack. How do I consider studies that make claims about percentages of people that fit into those categories? As extremely ambiguous in what they are actually indicating. Do Americans have a problem with weight? I think so. Does using false numbers to overestimate the problem help? I don't think so, especially when people realize the metrics leave a lot to be desired.
- viraptor 6y ago
  The measurements don't have to be precise to show a trend, relation, or infer a number of valid results. If someone calls the study into question based on using imperfect methods, rather than using those methods incorrectly... That's their opinion, but it's not useful.
  - kbenson 6y ago
    They don't have to be precise to show a trend, but there needs to be some assurance that the measurements affects subgroups similarly and a measurement of how it affects those subgroups to infer a number of valid results. How does BMI accuracy scale with age? How does it scale with different ethnic groups? How do these interact? How do you infer an accurate number without knowing these variables and accounting for them and the relative sized of those cohorts? If the measurements to create the BMI were taken from a statistically valid cross section of the current makeup of Americans, then I would have no problem. But how was the BMI generated? When? With what type of participants? This article itself notes that Asians experience relatively more problems at a lower BMI. Without knowing what the BMI is tuned to, how an we interpret how it applies to a cross section of Americans for a singular study? As a measurement of similar studies seeing a change over time, I agree it's less problematic (but could still be affected by trends in physiology over time, possibly from immigration).
- worik 6y ago
  The fallacy of applying statistical measures to individuals. That fallacy has a name, which I cannot recall
- tasty_freeze 6y ago
  We have an epidemic of overweight people. We can worry about misleading BMI stats when we have an epidemic of bodybuilders who worry they might actually be overweight.
  - kbenson 6y ago
    Isn't that exactly what I'm addressing? How using misleading or bad metrics can lead to a mistrust in what is being conveyed? Think "Reefer madness" and all the bunk science out about Marijuana in the 80's and 90's. Did anyone trust the information coming out at that time? I would hazard most in their teens and twenties didn't, which is exactly who that information was intended to sway. Trust is important. If people don't trust that what you're saying is accurate because it's easy to point out the shortcuts taken that muddy the results, I think eventually they are going to look at most results about that subject with a grain of salt. At that point they've been trained to do so. The best ammo against a problem is clear and accurate information. Not fear-mongering and FUD, or even something adjacent that's just imprecise enough to be easily called into question. All that does is cause confusion and arguments over veracity.
tokamak-teapot 6y ago
It should be an easy metric, yes. I think it does help some people realise they are in poor physical health. The problem with it is that it’s so commonly responded to with ‘muscle means it isn’t right’. I used to be fairly fit and fairly strong and a bit too much towards the ‘obese’ category. I remember semi-believing it was muscle pushing me up the scale that far. I’m now right in the middle of the ‘healthy weight’ category and I’d like to go back and convince my younger self that it’s time to fix the food intake and that muscle isn’t what’s pushing the weight up.
sieabahlpark 6y ago
> Yes, everyone realizes this already, and nobody who is in that position is going to be mislead into thinking they are obese. Not everyone would know by now if people didn't repeat it. Just because you know something don't expect all 7 billion other potential people to automatically know.
VanillaCafe 6y ago
You're not wrong that BMI is okay enough of a metric for most people. But, in terms of a metric that is even more simple (one simple measurement tool instead of two), accounts for athletic builds, and is arguably more predictive of health outcomes (example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071369/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071369/), it would be great if we could standardize on waist-to-hip ratio instead of BMI.
- t-writescode 6y ago
  Scales are common, fabric tape measures are rare; and, even men's jeans no longer correspond to their inch number. Learned that one the hard way this year.

kbenson 6y ago

> Yes, everyone realizes this already, and nobody who is in that position is going to be mislead into thinking they are obese. No, but someone who works out the numbers and realizes that the BMI doesn't match them well, or their circumstances well, realizes it calls the study and what it represents into question. Using controversial metrics because they are easily available is counter-productive in the long run, because once people realize you were misrepresenting your credibility is lost. At best it's lazy. Right now I'm obese. In high school according to the BMI I was almost half-way through overweight edging towards obese, and that was with very little fat, a very active lifestyle, and a visible six-pack. How do I consider studies that make claims about percentages of people that fit into those categories? As extremely ambiguous in what they are actually indicating. Do Americans have a problem with weight? I think so. Does using false numbers to overestimate the problem help? I don't think so, especially when people realize the metrics leave a lot to be desired.

viraptor 6y ago
The measurements don't have to be precise to show a trend, relation, or infer a number of valid results. If someone calls the study into question based on using imperfect methods, rather than using those methods incorrectly... That's their opinion, but it's not useful.
- kbenson 6y ago
  They don't have to be precise to show a trend, but there needs to be some assurance that the measurements affects subgroups similarly and a measurement of how it affects those subgroups to infer a number of valid results. How does BMI accuracy scale with age? How does it scale with different ethnic groups? How do these interact? How do you infer an accurate number without knowing these variables and accounting for them and the relative sized of those cohorts? If the measurements to create the BMI were taken from a statistically valid cross section of the current makeup of Americans, then I would have no problem. But how was the BMI generated? When? With what type of participants? This article itself notes that Asians experience relatively more problems at a lower BMI. Without knowing what the BMI is tuned to, how an we interpret how it applies to a cross section of Americans for a singular study? As a measurement of similar studies seeing a change over time, I agree it's less problematic (but could still be affected by trends in physiology over time, possibly from immigration).
worik 6y ago
The fallacy of applying statistical measures to individuals. That fallacy has a name, which I cannot recall
tasty_freeze 6y ago
We have an epidemic of overweight people. We can worry about misleading BMI stats when we have an epidemic of bodybuilders who worry they might actually be overweight.
- kbenson 6y ago
  Isn't that exactly what I'm addressing? How using misleading or bad metrics can lead to a mistrust in what is being conveyed? Think "Reefer madness" and all the bunk science out about Marijuana in the 80's and 90's. Did anyone trust the information coming out at that time? I would hazard most in their teens and twenties didn't, which is exactly who that information was intended to sway. Trust is important. If people don't trust that what you're saying is accurate because it's easy to point out the shortcuts taken that muddy the results, I think eventually they are going to look at most results about that subject with a grain of salt. At that point they've been trained to do so. The best ammo against a problem is clear and accurate information. Not fear-mongering and FUD, or even something adjacent that's just imprecise enough to be easily called into question. All that does is cause confusion and arguments over veracity.

tokamak-teapot 6y ago

It should be an easy metric, yes. I think it does help some people realise they are in poor physical health. The problem with it is that it’s so commonly responded to with ‘muscle means it isn’t right’. I used to be fairly fit and fairly strong and a bit too much towards the ‘obese’ category. I remember semi-believing it was muscle pushing me up the scale that far. I’m now right in the middle of the ‘healthy weight’ category and I’d like to go back and convince my younger self that it’s time to fix the food intake and that muscle isn’t what’s pushing the weight up.

sieabahlpark 6y ago

> Yes, everyone realizes this already, and nobody who is in that position is going to be mislead into thinking they are obese. Not everyone would know by now if people didn't repeat it. Just because you know something don't expect all 7 billion other potential people to automatically know.

VanillaCafe 6y ago

You're not wrong that BMI is okay enough of a metric for most people. But, in terms of a metric that is even more simple (one simple measurement tool instead of two), accounts for athletic builds, and is arguably more predictive of health outcomes (example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071369/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071369/), it would be great if we could standardize on waist-to-hip ratio instead of BMI.

t-writescode 6y ago
Scales are common, fabric tape measures are rare; and, even men's jeans no longer correspond to their inch number. Learned that one the hard way this year.